Before a pair of long-tailed tits (Aegithalos caudatus) set out to make their nest, first they block out a month of time, and then they go about collecting the materials on their shopping list: - 600+ silk spider cocoons - 3,000 lichen flakes - 1,500 feathers - 200-300 sprigs of moss

This is what Mike Hansell, of Glasgow University, painstakingly determined was needed for the Eurasian bird to build a typical nest, one of the most beautifully formed and skillfully constructed nests in the world.

It takes up to two weeks to build the shell of the structure using the "Velcro principle" of intricate loops of spider cocoon silk wound around bits of moss to support the walls, which can be adjusted for expansion. Another two weeks are needed to line the 5" nest with a comfortable layer of feathers.